Method for preservation of fish

ABSTRACT

A method for preservation of fish consists in that the original product is salt-cured and held, whereupon the fish is given a protective coating of a polymer composition containing polyvinyl alcohol, a mixture of poly-hydroxyethyleneglycol ethers of monoethanolamides of synthetic fatty acids of the C 10  -C 16  fraction, sorbic acid, glycerol and water, the mass percentage content of the components of said polymer composition being as follows: 
     
         ______________________________________                                    
 
    
     polyvinyl alcohol       0.1 to 25.0                                       
mixture of polyhydroxyethyleneglycol                                      
                        0.00024 to 0.06                                   
ethers of monoethanolamides of synthetic                                  
fatty acids of the C 10  -C 16  fraction                            
sorbic acid             0.01 to 4.0                                       
glycerol                10 to 15                                          
water                   to make up 100,                                   
______________________________________                                    
 
     whereupon the thus-obtained coated fish is treated with an aqueous modifying solution of the following mass percentage composition:______________________________________modifier           1 to 25water              to make up 100.______________________________________

FIELD OF THE ART

The present invention relates to methods for preservation of foodproducts.

PRIOR ART

One prior-art method for preservation of balyk (i.e., cured fillet ofsturgeon or salmon) semiproduct consists in application of common saltto its surface, placing the semiproduct in salt-curing vats, filling-inwith a saturated sodium chloride solution, keeping till a required saltcontent, removing from the salt solution, washing off undissolved saltand holding on rack stands for a uniform salt distribution in the fleshof the fish. Upon holding (attaining uniform salt content) thethus-salted balyk semiproduct is put in storage. To this end the saltedbalyk semiproduct is placed in containers, filled-in with an aqueouscommon salt solution having a density of 1.11 to 1.14 g/cm³ and storedat minus 2° to minus 8° C. (cf. T. I. Makarova, A. I. Tinyakova,"Collected technological instructions on fish processing", Moscow,Pishchevaya promyshlennost' Publishers, 1980, v. 2, pp. 63 to 67 (inRussian).

For a better quality of a salted balyk semiproduct in the course ofstorage in a common salt solution, some antioxidants of the class ofgallates, butylhydroxytoluene, and butylhydroxy-anisole are known to beadded to that solution (cf. L. I. Yudina, "Application of antioxidantsto prevent fat oxidation in pickled Atlantic herring", Moscow, TrudyVNIRO (Proceedings of the USSR Marine Fisheries and OceanographyResearch Institute, 1962, v. 45, pp. 32 to 35).

However, the aforementioned methods suffer from a number of cardinaldisadvantages:

washing of nitrogen-containing protein substances and lipids from asalted balyk semiproduct when stored in an aqueous common-salt solution,which results in a reduced nutritive value of the product;

swelling of muscular tissue which occurs with a salted balyk semiproductwhen stored in the aforesaid solution, affects adversely the quality ofthe product and leads to a considerable loss of the product mass duringsubsequent storage;

transportation of the semiproduct in containers filled with the saltsolution involves unjustified use of hauling facilities due to aconsiderable mass of the solution and the containers.

The invention has for its object to provide such a method forpreservation of a balyk semiproduct that would make it possible toretain its nutritive value, and eliminate loss of its protein and lipidcomponents.

DESCRIPTION OF THE INVENTION

The object is accomplished due to the fact that there is provided amethod for preservation of a balyk semiproduct by salt-curing andholding the original product, and there-after, according to theinvention, applying to the balyk semiproduct after holding a protectivecoating of a polymer composition containing polyvinyl alcohol, a mixtureof polyhydroxyethyleneglycol ethers of monoethanolamides of syntheticfatty acids of the C₁₀ -C₁₆ fraction sorbic acid, glycerol, water, themass percentage content of the components of said polymer compositionbeing as follows:

    ______________________________________                                        polyvinyl alcohol       0.1 to 25.0                                           mixture of polyhydroxyethyleneglycol                                                                  0.00024 to 0.06                                       ethers of monoethanolamides of synthetic                                      fatty acids of the C.sub.10 -C.sub.16 fraction                                sorbic acid             0.01 to 4.0                                           glycerol                10 to 15                                              water                   to make up 100,                                       ______________________________________                                    

whereupon the semiproduct together with the protective coating istreated with an aqueous modifying solution of the following masspercentage composition:

    ______________________________________                                        modifier           1 to 25                                                    water              to make up 100.                                            ______________________________________                                    

It is desirable that use be made of boric acid and salts thereof as wellas water-soluble metal chlorides as the modifier.

BEST MODE OF CARRYING THE INVENTION INTO EFFECT

The method of the invention is carried into effect as follows.

The essence of the method of preservation of a balyk semiproduct residesin that an original fishery product is subjected to salt-curing,holding, whereupon the original product is given a protective coating ofa polymer composition either by dipping in or spraying with saidcomposition. The polymer composition used features the following masspercentage content of its components:

    ______________________________________                                        polyvinyl alcohol       0.1 to 25                                             mixture of polyhydroxyethyleneglycol                                                                  0.00024 to 0.06                                       ethers of monoethanolamides of synthetic                                      fatty acids of the C.sub.10 -C.sub.16 fraction                                sorbic acid             0.01 to 4.0                                           glycerol                10 to 15                                              water                   to make up 100.                                       ______________________________________                                    

Used as a modifying solution is the one having the following masspercentage composition:

    ______________________________________                                        modifier           1 to 25                                                    water              to make up 100.                                            ______________________________________                                    

Boric acid and salts thereof, as well as water-soluble metal chlorides.

The presence of sorbic acid in the formulation of the composition as astructure-forming preservative provides for a preservative effect and atthe same time promotes the formation of a coating on the surface of theproduct by virtue of additional structurization of the polymer.

The mixture of polyhydroxyethyleneglycol ethers of monoethanol-amides ofsynthetic fatty acids of the C₁₀ -C₁₆ fraction, which is authorized forcontact with foodstuffs, is used as a surfactant. The presence of thesurfactant in the formulation of the composition provides for an optimumhydrophilic-hydrophobic balance in formation of a coating onfat-containing products. Formation of a coating which possesses acomplex of properties that provide for retention of the quality of theproduct while under storage, does not occur unless the composition andthe modifying solution contain all of the aforementioned components.

The thus-coated product is kept under storage at minus 2° to minus 8° C.

Application of a polyvinyl alcohol solution with a concentration below0.1 percent fails to provide a continuous coating over the entiresurface of the product, whereas such solutions with a concentration of25.5 percent and over are liable to rapidly congeal under routineproduction conditions and to form clumps on the surface of the product.

The surfactant features a critical concentration of micelle-formationequal to 0.00024 mass percent. When the surfactant used has the value ofa micelle-formation concentration below the critical, the solution failsto possess a required surface tension value for a flawless coating toform, whereas application of the surfactant with a micelle-formationconcentration above 0.6 mass percent disturbs a requiredhydrophilic-hydrophobic balance.

Application of sorbic acid in concentrations below 0.01 mass percentfails to produce a required preserving and structurizing effect, whileits concentrations higher than 4 mass percent cannot be used due tolimited solubility of the acid in the system.

Adding the plasticizer to the modifying solution in an amount of 9 masspercent or less fails to provide a required plasticizing effect, whereasits mass percentage content equal to 16 or more deteriorates the qualityof the coating obtained.

Application of the modifier in an amount of 0.9 mass percent or lessfails to provide a structurizing effect of the system, whereasintroducing the modifier in an amount of 25.5 mass percent and over isunreasonable from technological viewpoint, since surplus of thestructuring agent deteriorates the quality of the coating (renders itbrittle).

Some specimens of salt-cured balyk semiproduct prepared from sturgeonaccording to the method of the invention and provided with a protectivecoating, as well as a salt-cured balyk semiproduct made of sturgeon andkept stored in a common salt solution, were subjected to organolepticassessment after they had been kept under storage within a six-monthperiod at minus 2° to minus 8° C. It is found out that the specimen ofsalt-cured balyk semiproduct kept stored in a coating from the polymercomposition according to the invention, is superior, as to itsorganoleptic characteristics, to that stored in a common-salt solution.The balyk semiproduct that has been stored in a common-salt solutionexhibits on its surface a deposit of oxidized fat having a specificodour, its tissues being flabby and showing stratification. Somecongealed lipids are observed on the surface of the common-salt solutionthat have separated out of the product. After a six-month storage theproduct is degraded into the second grade on account of fat oxidation.The specimens of the semiproduct that have been stored for six monthsaccording to the method of the invention, feature succulent consistency.The quality of balyk semiproduct kept under storage according to themethod of the invention is bettered, as compared with that storedaccording to the known method, due to its being free from stratificationof muscular tissue.

As it has been demonstrated by special studies, the processes ofaccumulation of primary and secondary oxidation products in the lipidsof the balyk semiproduct (i.e., peroxide, aldehyde and acid values),proceed at a much slower rate in the semiproduct stored according to themethod of the invention as compared with the known method.Water-retaining property of the muscular tissue is better maintained inthe semiproduct when stored according to the method of the inventionthan in that stored according to the known method. When the semiproductis stored in a common-salt solution, its muscular tissue is observed tohave swollen badly (by 32 percent), the protein and lipid componentsthereof being washed out to a great extent, which affects adversely thenutritive value of balyk as the finished product. Storage of balyksemiproduct according to the method of the invention retains itsnutritive value and mass due to the components of its tissues being notwashed out therefrom.

For a better understanding of the present invention the followingillustrative examples of its practical embodiment are given hereinbelow.

EXAMPLE 1

20 kg of sturgeon sides chilled to minus 2° C. is rubbed with NaCl,placed in a salt-curing vat and poured with a filtered-out common-saltsolution having a density of 1.2 g/cm³ and chilled to minus 2° C. Aftersalt-curing the fishery product is discharged from the vats, washed witha common-salt solution with a density of 1.07 g/cm³ and placed on rackstands at a maximum temperature of plus 10° C. to attain a uniform saltcontent. After a two-day holding the thus-obtained salt-cured balyksemiproduct is coated with a polymer composition of the following masspercentage content of its components:

    ______________________________________                                        polyvinyl alcohol     0.1                                                     mixture of polyhydroxyethyleneglycol                                                                0.00024                                                 ethers of monoethanolamides of synthetic                                      glyceric acids of the C.sub.10 -C.sub.16 fraction                             sorbic acid           0.01                                                    glycerol              10                                                      water                 to make up 100.                                         ______________________________________                                    

Thereupon the product covered with the aforesaid coating is immersed ina modifying bath, containing a solution of the following mass percentagecontent:

    ______________________________________                                        boric acid    1                                                               water         to make up 100.                                                 ______________________________________                                    

Then the semiproduct is taken out of the bath and stored at minus 2° tominus 8° C.

EXAMPLE 2

A salt-cured balyk semiproduct obtained as in Example 1, is coated witha polymer composition of the following mass percentage content:

    ______________________________________                                        polyvinyl alcohol    25                                                       mixture of polyhydroxyethylene-                                                                    0.06                                                     glycol ethers of monoethanolamides                                            of synthetic glyceric acids of the                                            C.sub.10 -C.sub.16 fraction                                                   sorbic acid          4.0                                                      glycerol             15                                                       water                to make up 100.                                          ______________________________________                                    

Then the semiproduct is treated with a modifying composition of thefollowing mass percentage content:

    ______________________________________                                        NaCl        25                                                                Water       to make up 100.                                                   ______________________________________                                    

Thereupon the thus-coated semiproduct is stored as in Example 1.

EXAMPLE 3

A salt-cured balyk semiproduct obtained as in Example 1, is coated witha polymer composition of the following mass percentage content:

    ______________________________________                                        polyvinyl alcohol        10                                                   mixture of polyhydroxyethyleneglycol                                                                   0.03                                                 glyceric acids of the C.sub.10 -C.sub.16 fraction                             sorbic acid              0.15                                                 glycerol                 12                                                   water                    to make up 100.                                      ______________________________________                                    

Then the semiproduct is treated with a modifying composition of thefollowing mass percentage content:

    ______________________________________                                        CaCl.sub.2  20                                                                water       to make up 100.                                                   ______________________________________                                    

Thereupon the thus-coated semiproduct is kept under storage as inExample 1.

EXAMPLE 4

A salt-cured balyk semiproduct obtained as in Example 1 is coated with apolymer composition of the following mass percentage content:

    ______________________________________                                        polyvinyl alcohol    10                                                       mixture of polyhydroxyethylene-                                                                    0.03                                                     glycol ethers of monoethanolamides                                            of synthetic glyceric acids of the                                            C.sub.10 -C.sub.16 fraction                                                   sorbic acid          0.15                                                     glycerol             10                                                       water                to make up 100.                                          ______________________________________                                    

Then the semiproduct is treated with a modifying composition of thefollowing mass percentage content:

    ______________________________________                                        sodium borate 3                                                               water         to make up 100.                                                 ______________________________________                                    

Thereupon the thus-coated semiproduct is stored as in Example 1.

EXAMPLE 5

A salt-cured balyk semiproduct obtained as in Example 1 is coated with apolymer composition of the following mass percentage content:

    ______________________________________                                        polyvinyl alcohol    10                                                       mixture of polyhydroxyethylene-                                                                    0.03                                                     glycol ethers of monoethanolamides                                            of synthetic glyceric acids of the                                            C.sub.10 -C.sub.16 fraction                                                   sorbic acid          0.15                                                     glycerol             12                                                       water                to make up 100.                                          ______________________________________                                    

Then the semiproduct is treated with a modifying composition of thefollowing mass percentage content:

    ______________________________________                                        Boric acid    2                                                               Water         to make up 100                                                  ______________________________________                                    

Thereupon the thus-coated semiproduct is stored as in Example 1.

INDUSTRIAL APPLICABILITY

The method of preservation of a balyk semiproduct may find applicationin the production and storage of fish and fishery products.

What is claimed is:
 1. A method for preservation of fish, whichcomprises coating the fish with a protective coating of a polymercomposition containing polyvinyl alcohol, a mixture ofpolyhydroxyethyleneglycol ethers of monoethanolamides of synthetic fattyacids of the C₁₀ -C₁₆ fraction, sorbic acid, glycerol and water, theweight percentage content of the components of said polymer compositionbeing as follows:

    ______________________________________                                        polyvinyl alcohol       0.1 to 25.0                                           mixture of polyhydroxyethyleneglycol                                                                  0.00024 to 0.06                                       ethers of monoethanolamides of synthetic                                      fatty acids of the C.sub.10 -C.sub.16 fraction                                sorbic acid             0.01 to 4.0                                           glycerol                10 to 15                                              water                   to make up 100,                                       ______________________________________                                    

whereupon the coated fish is treated with an aqueous modifying solutionof the following weight percentage composition:

    ______________________________________                                        modifier           1 to 25                                                    water              to make up
 100.                                            ______________________________________                                    


2. A method as claimed in claim 1, wherein the modifier comprises amember selected from the group consisting of boric acid, salts of boricacid and water-soluble metal chlorides.
 3. The method of claim 2,wherein the modifier is selected from the group consisting of sodiumchloride, calcium chloride, sodium borate and boric acid.